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261.
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I. Markiewicz W. G. Strupczewski K. Kochanek V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(6):391-405
Three dispersion measures of a random variable, i.e., the standard deviation, the mean deviation (MD) about the mean and the second L-moment, are analyzed in terms of their properties and mutual relationships. Emphasis is placed on the MD, as it is less recognized than two other dispersion measures. The relationships between the dispersion measures are derived for distributions commonly applied in flood frequency analysis (FFA). For distributions that are unbounded, there is a distribution-dependent constant value of the ratio of dispersion measures, or equivalently of respective coefficients of variation. For two-parameter distributions that are lower-bounded, the relationship between the coefficients of variation is also distribution dependent and is not linear. For lower-bounded three-parameter distributions, the dispersion measure ratios, or equivalently the ratios of coefficients of variation, depend on the coefficient of skewness and show a strong distributional dependence. For selected distributions, the three dispersion measures are compared both in terms of the robustness to the largest samples element and the accuracy of upper quantile estimation. The MD statistics may be highly competitive to the two other dispersion measure statistics if applied in FFA for parameters estimation. 相似文献
263.
The Harvard CMT catalogue contains 481 shallow earthquakes that occurred between 1 January 1977 and 30 November 2005 within
a broad region defined by the geographical latitude from 3°S to 14°N and by the longitude from 91°E to 102°E. There are 230
events that occurred before the great earthquake of 26 December 2004. Their surface distribution is not uniform and the source
area of the 2004 great event appears as an area of seismic quiescence with a radius of about 100 km. There are 186 events
that occurred between the two great earthquakes of 26 December 2004 and 28 March 2005. Practically all of them are located
to the northwest from the great earthquake of 2005, that in turn was followed by 63 events, mostly located to the southeast.
The cumulative seismic moment from earthquakes before the occurrence of the great event of 2004 increased rather regularly
with time, with sudden increase about twenty years and two years before the occurrence of the great event. The seismic moment
of earthquakes between the two great events increased rapidly during the first ten-fifteen days, then flattened out and increased
slowly with time. After the great event of 2005 the seismic moment shows quiet increase during some 115 days, then sudden
jump, followed by very small activity till the end of our observations. From the spatial distribution of seismic moment of
earthquakes that occurred before the great event of 2004 it follows that its largest release appeared to the southeast from
the great event, around the rupture area of the great earthquake of 2005. The largest release of seismic moment from earthquakes
between the two great events is observed in the vicinity of the 2004 event and further up to the north. The seismic moment
from earthquakes that occurred after the great event of 2005 was mostly released in its vicinity and further down to the south. 相似文献
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鲜水河断裂带是四川西部一条晚第四纪强烈左旋走滑活动的构造带,历史上发生多次强震. 它与西北侧的甘孜—玉树断裂带一起,构成青藏高原东部的侧向滑移构造系统中的川滇活动地块的北边界——羌塘地块的东北边界. 鲜水河断裂带北西段可以分成4个段落,每一段落均可作为一个独立的基本破裂单元而发生地震破裂,亦有可能发生不同尺度的多段联合瞧裂. 对鲜水河断裂带北西段不同尺度破裂的震级及复发间隔进行研究. 根据该地区的地质、地球物理、测量及地震等方面的资料,结合我国强震复发的特点,分析了拉分盆地内部的滑动速率分布,以确定各段落的等效长度和倾向宽度,从而建立适合我国大陆走滑断裂的面波震级与断裂发震面积的关系式;进而运用地震矩方法,考虑断层之间的相互作用,结合专家意见建立了该段的矩平衡断裂破裂模型;最后,给出了鲜水河断裂带北西段各破裂源特征化地震的复发间隔、震级大小和不确定性,以及他与中小地震的联合震级分布. 结果表明,鲜水河断裂带北西段较易发生单段破裂,复发间隔在100~150年左右. 相似文献
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分析了福州三山视线控制线规划,采用了基础空间数据和ArcGIS 9.0平台,实现了快速建立数字高程模型与建筑物三维框架模型. 相似文献
270.
In this study, we documented the Holocene history of a peat plateau at the arctic tree line in northern Québec using stratigraphic and macrofossil analyses to highlight the effects of geomorphic setting in peatland development. Paludification of the site began about 6800 cal yr BP. From 6390 to 4120 cal yr BP, the peatland experienced a series of flooding events. The location of the peatland in a depression bounded by two small lakes likely explains its sensitivity to runoff. The proximity of a large hill bordering the peatland to the south possibly favored the inflow of mineral-laden water. The onset of permafrost aggradation in several parts of the peatland occurred after 3670 cal yr BP. Uplifting of the peatland surface caused by permafrost stopped the flooding. According to radiocarbon dating of the uppermost peat layers, permafrost distribution progressed from the east to the west of the peatland, indicating differential timing for the initiation of permafrost throughout the peatland. Most of the peatland was affected by permafrost growth during the Little Ice Age. Picea mariana macroremains at 6450 cal yr BP indicate that the species was present during the early stages of peatland development, which occurred soon after the sea regression. 相似文献